1. Field of the Invention
The invention concerns an electronic entity with a magnetic antenna.
2. Description of the Related Art
Electronic entities of this type generally comprise an electronic circuit having in particular two terminals to which is connected a magnetic antenna generally formed of a winding of several turns produced in conductive material.
This type of electronic entity includes in particular contactless microcircuit cards (where the magnetic antenna constitutes the only means of communication of the microcircuit with the exterior) and so-called “dual” or “hybrid” microcircuit cards (where electrical contacts are provided on one face of the card that provide an alternative mode of communication of the microcircuit with the exterior). In microcircuit cards of either type, the turns of the magnetic antenna are generally produced in the form of windings of copper wire or conductive tracks, in both cases disposed within the layers physically constituting the card.
It can also be a question of an electronic entity of the electronic passport type that comprises in one of its pages means (in particular microcircuit and antenna means) able to communicate without contact with an external device of the reader type.
In all cases, to increase the induced current that the magnetic antenna delivers to the electronic circuit, the designer of the electronic entity is constrained to increase the number of turns in order to increase the magnetic flux through the antenna.
Increasing the number of turns rapidly leads to problems, however: on the one hand, the increase of the area that carries the turns relative to the available area can cause problems of congestion, all the more so in that the geometry of the turns is relatively fixed, which is a particular nuisance in the case of electronic entities with small dimensions; on the other hand, the small number of areas generally available to receive the turns (often deposited in the same plane, for example) make bridging techniques necessary for the looping of the electrical circuit, as described for example in patent application FR 2 769 390.